Initial accounts of the Yala attack cited three blasts with explosives planted in cars and motorcycles, but officials later corrected themselves.

In October last year, suspected militants staged coordinated attacks at more than 30 spots across Yala city, killing three people and injuring more than 50. A month earlier, a trio of bombs hidden in vehicles hit a busy section of Sungai Kolok in Narathiwat province, killing four people and leaving more than 60 wounded.

Thai authorities have imposed a state of emergency since 2005 that gives security forces special powers to arrest and detain suspects in the three provinces. But the decree and a massive security presence have failed to curb the violence and little is known about the militants or their goals.

The insurgents have made no public pronouncements but are thought to be fighting for an independent Muslim state. The area used to be an Islamic sultanate until it was annexed by Thailand in the early 20th century.

Yala, Narathiwat and Pattani are the only Muslim-dominated provinces in the predominantly Buddhist country. Muslims in the area have long complained of discrimination by the central government.